01 / TANBIR SAROWAR
Measure.Understand.
Precision metrology for semiconductor manufacturing and advanced packaging. Current work in the Precision Metrology & Instrumentation Group at Texas A&M University.
CURRENT LAB · ADVISED BY DR. CHABUM LEE
The wafer–chuck interface
The wafer–chuck interface establishes a reference surface for semiconductor processing. My doctoral research measures its air gap and contact state without damaging the wafer.
- Introduced electrochemical impedance spectroscopy using a magnetic ball-ended probe and an equivalent-circuit representation of the contact, wafer, and air gap.
- Measured vacuum-induced gap closure with near-infrared reflection spectroscopy and Fabry–Pérot fringe analysis, cross-validated using a capacitive sensor.
- Connects experimental measurements with plate mechanics and squeeze-film flow models.
High-speed optical deflectometry
A non-contact optical system maps the shape of a 300 mm wafer and captures the transient as it seats on a vacuum chuck.
- Built a dot-pattern deflectometry system with camera and homography calibration, sub-pixel dot localization, and slope-to-height reconstruction.
- Developed flip and rotation-reversal decomposition to separate gravity sag, intrinsic warpage, and chuck systematic error.
- Extended acquisition to 2,100 frames per second, resolving an overdamped elastohydrodynamic relaxation controlled by the wafer–chuck seal.
Non-destructive bonded-wafer inspection
Wafer-level assessment of bond quality in SiCN-bonded wafers, in collaboration with Samsung Electronics.
- Characterized 300 mm bonded wafers using magnetic-probe EIS over 10 Hz–100 MHz.
- Mapped bond quality on 7 × 7 grids and a 37-point polar sampling scheme, tracking annealing-related changes in interfacial resistance.
- Located high-impedance candidate defects and checked them with NIR imaging to connect global screening with local inspection.
Metrology for repair engineering
A repair engineering framework links measurement of geometry and material properties with diagnosis, reverse design, and additive repair.
- Examines the measurement information required to diagnose damage and support repair decisions.
- Connects 3D CAD data, surface and material properties, and dynamic models with corrective and preventive repair strategies.
EARLIER RESEARCH · WASHINGTON STATE UNIVERSITY
Designing microfluidics
with data.
My master’s research with Dr. Xiaolin Chen paired validated COMSOL simulations with supervised learning to design deterministic lateral displacement devices for circulating tumor cell separation.
A random-forest model achieved a test R² of 0.994 and a mean absolute error of 0.31 µm in critical diameter. Surrogate-guided optimization identified a design in 2.3 seconds, with a targeted CFD simulation used for confirmation.
Related work explored dielectrophoresis-assisted inertial separation in curved contraction-expansion microchannels. Earlier undergraduate projects investigated liquid-metal-cooled heat sinks and ceramic substrates.
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